Crystal structure of an L-type lectin domain from archaea.

The crystal structures of an L-type lectin domain from Methanocaldococcus jannaschii in apo and mannose-bound forms have been determined. A thorough investigation of L-type lectin domains from several organisms provides insight into the differences in these domains from different kingdoms of life. While the overall fold of the L-type lectin domain is conserved, differences in the lengths of the carbohydrate-binding loops and significant variations in the Mn2+ -binding site compared to the Ca2+ -binding site are observed. Furthermore, the sequence and phylogenetic analyses suggest that the archaeal L-type lectin domain is evolutionarily closer to the plant legume lectins than to its bacterial or animal counterparts. This is the first report of the biochemical, structural, sequence, and phylogenetic analyses of an L-type lectin domain from archaea and serves to enhance our understanding of the species-specific differences and evolution of L-type lectin domains.

Conformational Differences Unfold a Wide Range of Enterotoxigenic Abilities Exhibited by rNSP4 Peptides from Different Rotavirus Strains.

NSP4 has been recognized as the rotavirus-encoded enterotoxin. However, a few studies failed to support its diarrheagenic activity. As recombinant NSP4 (rNSP4) peptides of different lengths were used in the limited number of studies, a comparison of relative diarrheagenic potential of NSP4 from different strains could not be possible. To better understand the diarrheagenic potential of NSP4 from different strains, in this report we have evaluated the enterotoxigenic activity of the deletion mutant ΔN72 that lacks the N-terminal 72 residues and the biologically relevant ΔN112 peptide which when derived from SA11 rotavirus strain were previously shown to be highly diarrheagenic in newborn mice. Detailed comparative analysis of biochemical and biophysical properties and diarrheagenic activity of the recombinant ΔN72 peptides from seventeen different strains under identical conditions revealed wide differences among themselves in their resistance to trypsin cleavage, thioflavin T (ThT) binding, multimerization and conformation without any correlation with their diarrhea inducing abilities. These results support our previously proposed concept for the requirement of a unique conformation for optimal biological functions conferred by cooperation between the N- and C-terminal regions of the cytoplasmic tail.